Circadian and stimulated thyrotropin secretion in cranially irradiated adult cancer survivors.

2.50
Hdl Handle:
http://hdl.handle.net/10541/76450
Title:
Circadian and stimulated thyrotropin secretion in cranially irradiated adult cancer survivors.
Authors:
Darzy, Ken H; Shalet, Stephen M
Abstract:
CONTEXT: It has been claimed that with the use of the TRH test and knowledge of the nocturnal TSH surge, the diagnosis of so-called hidden central hypothyroidism might be uncovered in a substantial proportion of euthyroid cranially irradiated children. STUDY SUBJECTS: We conducted 24-h TSH profiles and TRH tests in 37 euthyroid adult cancer survivors 2-29 yr (median, 11.5) after irradiation (18-64 Gy) and in 33 matched normal controls. RESULTS: Basal and stimulated TSH levels (during the TRH test) were significantly (P < 0.05) higher in the patients who had received craniospinal irradiation, more so in those with severe GH deficiency. Six patients (16%) had a hypothalamic TSH response to TRH. The maximum TSH surge calculated from the highest peak (average of the highest three sequential samples) and the smallest nadir (average of the smallest three sequential samples) in the whole 24-h profile period was above the cutoff value of 50% in all except one control subject and two patients. However, the nocturnal TSH surge was greatly reduced or absent in eight normal subjects (24%) and six patients (16%), not due to a genuine loss of diurnal rhythm, but simply to a shift in the timing of the peak TSH and/or the nadir TSH to outside the recommended sampling times (for the nocturnal surge) of 2200-0400 and 1400-1800 h, respectively; thereby potentially leading to an erroneous diagnosis of hidden central hypothyroidism. Overall, the maximum TSH surge was significantly (P = 0.01) reduced only in the GH-deficient patients (100.7 +/- 11%) compared with normal subjects (154.9 +/- 18.2%). Free T4 levels did not correlate with TSH surge results. CONCLUSIONS: The normality of free T4 levels and the wide discrepancy between the high rate of these TSH abnormalities and the very low rate of overt secondary hypothyroidism (3-6%) after prolonged periods of postirradiation follow-up strongly suggest that in the vast majority of patients, these abnormalities in TSH dynamics represent subtle functional disturbances in the hypothalamic-pituitary axis rather than genuine pathology that may progress with time. We suggest that in this context, use of the term hidden central hypothyroidism is inappropriate, because these subtle changes may not have any clinical significance.
Affiliation:
Department of Endocrinology, Christie Hospital, Wilmslow Road, Manchester M20 4BX, United Kingdom.
Citation:
Circadian and stimulated thyrotropin secretion in cranially irradiated adult cancer survivors. 2005, 90 (12):6490-7 J. Clin. Endocrinol. Metab.
Journal:
The Journal of Clinical Endocrinology and Metabolism
Issue Date:
Dec-2005
URI:
http://hdl.handle.net/10541/76450
DOI:
10.1210/jc.2005-1593
PubMed ID:
16204362
Type:
Article
Language:
en
ISSN:
0021-972X
Appears in Collections:
All Christie Publications

Full metadata record

DC FieldValue Language
dc.contributor.authorDarzy, Ken H-
dc.contributor.authorShalet, Stephen M-
dc.date.accessioned2009-08-06T11:37:31Z-
dc.date.available2009-08-06T11:37:31Z-
dc.date.issued2005-12-
dc.identifier.citationCircadian and stimulated thyrotropin secretion in cranially irradiated adult cancer survivors. 2005, 90 (12):6490-7 J. Clin. Endocrinol. Metab.en
dc.identifier.issn0021-972X-
dc.identifier.pmid16204362-
dc.identifier.doi10.1210/jc.2005-1593-
dc.identifier.urihttp://hdl.handle.net/10541/76450-
dc.description.abstractCONTEXT: It has been claimed that with the use of the TRH test and knowledge of the nocturnal TSH surge, the diagnosis of so-called hidden central hypothyroidism might be uncovered in a substantial proportion of euthyroid cranially irradiated children. STUDY SUBJECTS: We conducted 24-h TSH profiles and TRH tests in 37 euthyroid adult cancer survivors 2-29 yr (median, 11.5) after irradiation (18-64 Gy) and in 33 matched normal controls. RESULTS: Basal and stimulated TSH levels (during the TRH test) were significantly (P < 0.05) higher in the patients who had received craniospinal irradiation, more so in those with severe GH deficiency. Six patients (16%) had a hypothalamic TSH response to TRH. The maximum TSH surge calculated from the highest peak (average of the highest three sequential samples) and the smallest nadir (average of the smallest three sequential samples) in the whole 24-h profile period was above the cutoff value of 50% in all except one control subject and two patients. However, the nocturnal TSH surge was greatly reduced or absent in eight normal subjects (24%) and six patients (16%), not due to a genuine loss of diurnal rhythm, but simply to a shift in the timing of the peak TSH and/or the nadir TSH to outside the recommended sampling times (for the nocturnal surge) of 2200-0400 and 1400-1800 h, respectively; thereby potentially leading to an erroneous diagnosis of hidden central hypothyroidism. Overall, the maximum TSH surge was significantly (P = 0.01) reduced only in the GH-deficient patients (100.7 +/- 11%) compared with normal subjects (154.9 +/- 18.2%). Free T4 levels did not correlate with TSH surge results. CONCLUSIONS: The normality of free T4 levels and the wide discrepancy between the high rate of these TSH abnormalities and the very low rate of overt secondary hypothyroidism (3-6%) after prolonged periods of postirradiation follow-up strongly suggest that in the vast majority of patients, these abnormalities in TSH dynamics represent subtle functional disturbances in the hypothalamic-pituitary axis rather than genuine pathology that may progress with time. We suggest that in this context, use of the term hidden central hypothyroidism is inappropriate, because these subtle changes may not have any clinical significance.en
dc.language.isoenen
dc.subjectBrain Canceren
dc.subject.meshAdolescent-
dc.subject.meshAdult-
dc.subject.meshBrain Neoplasms-
dc.subject.meshCase-Control Studies-
dc.subject.meshCircadian Rhythm-
dc.subject.meshCranial Irradiation-
dc.subject.meshFemale-
dc.subject.meshHuman Growth Hormone-
dc.subject.meshHumans-
dc.subject.meshHypothyroidism-
dc.subject.meshMale-
dc.subject.meshMiddle Aged-
dc.subject.meshSpinal Cord-
dc.subject.meshSurvivors-
dc.subject.meshThyrotropin-
dc.subject.meshThyrotropin-Releasing Hormone-
dc.subject.meshThyroxine-
dc.titleCircadian and stimulated thyrotropin secretion in cranially irradiated adult cancer survivors.en
dc.typeArticleen
dc.contributor.departmentDepartment of Endocrinology, Christie Hospital, Wilmslow Road, Manchester M20 4BX, United Kingdom.en
dc.identifier.journalThe Journal of Clinical Endocrinology and Metabolismen

Related articles on PubMed

All Items in Christie are protected by copyright, with all rights reserved, unless otherwise indicated.